Process for producing alkyl aryl compounds having a reduced 2-phenyl isomer content



United States Patent O PROCESS FOR PRODUCING ALKYL ARYL COM- POUNDS HAVING A REDUCED Z-PHENYL ISO- MER CONTENT Robert W. Wotring, Gene E. Nicks, William A. Wentworth, and Claude D. Butler, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware No Drawing. Filed Sept. 16, 1968, Ser. No. 760,068

Int. Cl. C07c 3/56 US. Cl. 260-671 11 Claims ABSTRACT OF THE DISCLOSURE An improved process is provided which produces straight-chain alkyl aryl compounds by alkylating the aromatic nuclei of aromatic compounds with partially chlorinated straight chain paraflins or straight chain olefins in the presence of an alkylation catalyst combination of a Friedel-Crafts alkylation catalyst and a catalyst modifier.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for producing alkyl aryl compounds. More particularly, this invention relates to a process for producing straight-chain alkyl aryl compounds having a reduced Z-phenyl isomer content. In another aspect, this invention relates to a method for producing straight chain alkylbenzenes having a reduced Z-phenyl isomer content which upon sulfonation produce sulfonate derivatives which are amenable to complete biodegradation.

Brief description of the prior art Soft type synthetic detergents that are completely and readily biodegradable have been increasingly displacing the traditional soaps in domestic cleaning applications in the United States. Alkylbenzene sulfonates are widely employed in the manufacture of the soft commercial detergent products. These alkylbenzene sulfonates are generally prepared by alkylating an aryl compound, such as benzene, with partially chlorinated normal paraffins or olefins in the presence of an alkylation catalyst, such as aluminum chloride, in order to form detergent alkylates which, upon sulfonation and neutralization, produce the alkyl aryl sulfonates employed as the soft type detergent in commercial detergent products. It is likewise known that the foam, wetting, and detergency properties of the sulfonated alkylbenzenes depend upon sulfonate position, phenyl position, and chain length. In general when the alkyl group is a straight chain of from about 12. to 14 carbon atoms, the preferred alkylbenzene products are those in which the phenyl group is attached near the center of the alkyl chain. However, when alkylating with a catalyst, such as aluminum chloride, some of the phenyl groups are attached in the 2 position on the alkyl chain thus producing a 2-pheny1 isomer which is objectionable for use in the commercial detergent products because of its relatively low water solubility. Thus, it is desirable to provide a method for producing straight-chain alkylbenzene type compounds in which the 2-phenyl isomer content is reduced and in which the phenyl group is attached in the vicinity of the center of the alkyl group under normal alkylating conditions and such a method would represent a significant advance in the art.

OBJECTS OF THE INVENTION An object of the present invention is to provide a process for producing straight-chain alkyl aryl compounds 3,509,225 Patented Apr. 28, 1970 p CC having a reduced 2-phenyl isomer content. Another object of the present invention is to provide a process for preparing straight-chain alkylbenzenes which have a reduced 2-phenyl isomer content and which are well suited for use as detergents when sulfonated to form alkylbenzene sulfonates. Another object of the invention is to provide a process for producing detergent alkylate compositions having reduced 2-pheny1 isomer content and which upon sulfonation produce effective detergent agents which are substantially completely biodegradable. These and other objects will become apparent to those skilled in the art from the reading of the following detailed description and appended claims.

SUMMARY OF THE INVENTION It has now been found that straight-chain alkyl aryl compounds, such as alkylbenzene, having a reduced 2- phenyl isomer content can be prepared by employing a modified Friedel-Craft catalyst. Broadly the process involves alkylating an aromatic compound, such as benzene, with partially chlorinated C to C straight-chain normal parafiins wherein from about 10 to 35 mole percent of the parafiins are chlorinated, or with C to C straight-chain olefins, in the presence of an alkylation catalyst combination of a Friedel-Crafts alkylation catalyst and an effective amount of a catalyst modifier wherein the Friedel-Crafts alkylation catalyst and the catalyst modifier are present in a mole ratio within the range of about 1:25 to 2:1, respectively. Preferably the catalyst modifier is selected from the group consisting of pyridine, phenanthrene, durene, mesitylene, zinc chloride, sulfuric acid, aluminum oxide, phosphorus trichloride, carbon tetrachloride, boron oxide, hexamethylbenzene, and mixtures thereof, and the Friedel Crafts alkylation catalyst is aluminum chloride.

It has also now been found that straight-chain alkyl aryl compounds, such as alkylbenzene, having a reduced 2-phenyl isomer content can be prepared by alkylating an aromatic compound with partially chlorinated C to C straight-chain normal paraffins wherein from about 10 to 35 mole percent of the paraflins are chlorinated, or with C to C straight-chain olefins, in the presence of an alkylation catalystcombination of aluminum chloride and a sulfonated styrene-divinyl benzene polymer catalyst modifier wherein the aluminum chloride alkylation catalyst and the sulfonated styrene-divinyl benzene polymer catalyst modifier are present in a weight ratio of about 1:1 to 1:2, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, by following the teachings of the instant invention, it is possible to reduce the Z-phenyl isomer content of the alkylbenzenes obtained from normal alkylation by isomerizing alpha-olefins prior to alkylation or partially chlorinating the normal parafiins prior to alkylation and thereafter alkylating the chlorinated normal paraflins or isomerized alpha-olefins in the presence of an appropriate Friedel-Crafts catalyst and catalyst modifier combination. Thus, by reducing the Z-phenyl isomer content present in the resulting alkylbenzenes which when further processed into alkylbenzene sulfonates one produces a superior detergent product.

In the preparation of detergent alkylates from partially chlorinated normal parafiins, and as set forth in United States Patent No. 3,316,294 (1967) and hereby incorporated in part, a suitable normal paraffin mixture having from about 8 to 18 carbon atoms is partially chlorinated so as to produce largely mono-chlorinated normal paraffi ns. Either conventional liquid or vapor phase chlorinat1on of the parafiin can be employed. However, regardless of which of these chlorination techniques is employed, the degree of chlorination should be at least mole percent and not over 35 mole percent of the normal paraffins.

The ratio of chlorine to parafiin-to-be-chlorinated thereby can be varied over the range of from about 1:3 to 1:10, respectively, on the mole basis. However, it is preferred to operate at the ratio of about 1:5 moles of chlorine to parafiin from an economical standpoint because use of the very low amounts of chlorine necessitates excessive recycling of the paraffin. After suitably chlorinating the parafiin mixture, the halogenated product is then purged of by-product HCl and unreacted chlorine. Purg ng can be readily accomplished through the use of an inert gas, such as, for example, nitrogen.

For vapor phase thermal chlorination, temperatures of 230350 C. are operable. However, more important than temperature are the space velocity and residence time. In order to avoid uncontrolled combustion type reaction of chlorine and alkane, a linear velocity of at least about 88 feet per second is necessary. At this high velocity a residence time of about .5 to 1 second will give good conversion of reactants to products.

Liquid phase chlorination temperatures that can be used range from about room temperature to about 200 C. With photo chemical or other catalysis, lower temperature can be used and still obtain good reaction rates. It must be remembered that chlorination of an alkane is an exothermic reaction, consequently when it is desired to conduct the reaction at any particular temperature, the reaction should be initiated at a temperature sufficiently below that ultimately desired in order to compensate for the increase in temperature which will result as a consequence of the heat of reaction. The time for chlorination varies extensively and depends on the ratio of chlorine to parafiin used, temperature, etc. The time necessary to effect the desired degree of chlorination under any particular set of conditions can be readily determined experimentally. The chlorination product is then employed as the alkylatable component in the subsequent alkylation step.

Similarly, the detergent alkylates prepared by the present invention which have a reduced 2-phenyl isomer content can be prepared by the alkylation of an aromatic hydrocarbon, such as benzene, homologs of benzene, including toluene, ethyl benzene, xylene, isopropyl benzene, butylbenzene, etc., cumene and its homologs and naphthalene and its hOrnOlOgS, with olefins containing about 5 to 18 carbon atoms, such as ethylene isobutylene, hexylene, octylene, dodecene, and the like. Such a process is set forth in United States Patent No. 3,118,956 (1964), which is hereby incorporated in this application.

In the alkylation step for producing a detergent alkylate having a reduced Z-phenyl isomer content according to the present invention an aryl hydrocarbon compound is contacted with the partially chlorination n-paraffin, or olefin, as the case may be, in the presence of an appropriate catalyst combination composed of a Friedel-Crafts catalyst and a catalyst modifier. Appropriate Friedel-Crafts catalysts are those catalysts which form complexes with the catalyst modifier and which include activated aluminum chloride, activated aluminum bromide and boron trifluoride. The catalyst modifiers suitable for use in the present invention are pyridine, phenanthrene, durene, mesitylene, zinc chloride, sulfuric acid, aluminum oxide, phosphorus trichloride, carbon tetrachloride, boron oxide, hexamethylbenzene, and mixtures thereof, wherein the Friedel-Crafts alkylation catalyst and the catalyst modifier are present in a mole ratio within the range of about 1:25 to 2:1, respectively, and a sulfonated styrene-divinyl benzene polymer wherein the Friedel-Crafts alkylation catalyst and the sulfonated styrene-divinyl benzene polymer are present in a weight ratio of about 1:1 to 1:2. In most instances, the mole ratio of Friedel-Crafts alkylation catalyst to catalyst modifier is 1:25 to 2:1; however,

the use of ratios outside this range does not appear to adversely affect the alkylation of the aryl compound with the partially chlorinated normal paraffin or olefin.

Especially desirable results have been obtained in the alkylation of an aromatic compound with partially chlorinated straight-chain paraflins, or straight-chain olefins, wherein aluminum chloride is employed as the Friedel-Crafts alkylation catalyst constituent of the catalyst combination and where the mole ratio of the aluminum chloride to partially chlorinated normal parafiin, or olefin, is within the range of about 1: 15 to 1:30. When the catalyst modifier is selected from phenanthrene, durene, mesitylene, and zinc chloride desirable results have been obtained when the mole ratio of aluminum chloride alkylation catalyst and phenanthrene, durene, mesitylene, and zinc chloride is about 1:4. However, when the catalyst modifier is selected from pyridine or hexamethylbenzene, desirable results have been obtained wherein the aluminum chloride alkylation catalyst and the pyridine or hexamethylbenzene are present in a mole ratio of about 2:1.

Likewise, the catalyst modifier can be a combination of several catalyst modifiers thus providing a catalyst modifier having two or more components therein. When the catalyst modifier is composed of a two component mixture, desirable results have been obtained wherein one of the components is carbon tetrachloride and the other component is selected from the group consisting of phosphorus trichloride and boron oxide. When the catalyst modifier is a mixture of carbon tetrachloride and phosphorus trichloride, desirable results have been obtained when the aluminum chloride alkylation catalyst and the catalyst modifier combination of carbon tetrachloride and phosphorus trichloride are present in a mole ratio of about 1:20:5, respectively. However, when the catalyst modifier is a combination mixture of carbon tetrachloride and boron oxide, the mole ratio of aluminum chloride alkylation catalyst, carbon tetrachloride, and boron oxide are preferably present in a range of about 1:8:10, re spectively.

When the catalyst modifier employed is sulfuric acid, it is desirable that the aluminum chloride alkylation catalyst and sulfuric acid be present in a mole ratio of about 1:1, whereas when the catalyst modifier is aluminum oxide the aluminum chloride alkylation catalyst and aluminum oxide are present in a mole ratio of about 1:14. However, the mole ratios can vary over a wide range provided that the amount of catalyst modifier admixed with the alkylation catalyst is maintained below an amount which would completely deactivate the catalyst. However, as readily apparent, sufiicient catalyst modifier must be added to the alkylation catalyst in order to reduce its activity thus diminishing the formation of the undesirable 2-phenyl isomer portion in the finished detergent alkylate.

Another suitable catalyst modifier which can be employed in the process of the present invention is a sulfonated styrene divinyl benzene polymer, such as sold under the trade name Dowex WX4, manufactured and sold by Dow Chemical Company, Midland, Mich. However, due to the complexity of the polymer composition it is desirable that the modifier be specified by a Weight ratio rather than a mole ratio as in the catalyst modifiers discussed immediately above. Thus, the FriedeL Crafts alkylation catalyst, preferably aluminum chloride, and the catalyst modifier are preferably present in a weight ratio of about 1:1 to 1:2 in order to provide the resulting straight-chain alkyl aryl compound containing a reduced amount of an isomer having the aryl nucleus attached at the two position of the alkyl chain as provided by the present invention.

The catalyst modifier may be added to the catalyst prior to introduction into the alkylation zone or may be added prior to or subsequent to the addition of the catalyst into the alkylation zone. However, if the alkylation is a batch process it is preferred to introduce the catalyst modifier into the reaction zone prior to the addition of the catalyst. Such is especially desirable when using aluminum chloride because of the exothermic heat of mixing'which the catalyst undergoes with reactants. In a continuous process it is usually preferred to combine the catalyst and the catalyst modifier prior to their introduction into the alkylation zone.

In the alkylation step an aryl hydrocarbon compound is contacted with the partially chlorinated normal parafiin, or olefin, as the case may be, in the presence of the combination catalyst. The preferred Friedel-Crafts constituent of the catalyst combination is aluminum chloride. Benzene represents the preferred aryl compound for preparing detergent alkylates. However, other aromatic compounds, such as toluene, xylene, napthalene, and the like, can be used.

The alkylation temperature will vary, depending upon whether the alkylation agent is an alkyl halide or an olefin and upon the particular catalyst modifier employed in the catalyst combination. Generally, the temperature will rangefrom about room temperature to about 90 C.

6 EXAMPLE A series of experiments was conducted wherein a partially chlorinated C to C n-parafiin mixture wherein about 19 mole percent of the normal paraffins was chlorinated was employed to alkylate benzene in the presence of various combination catalysts. The benzene was dried by placing the benzene over sodiumribbon. In each experiment, the partially chlorinated parafiin, the henzene, and the catalyst modifiers were placed in a 500 ml. creased three-neck flask and the mole ratio of benzene to the chloroparaffin was about 8 to l. The aluminum chloride, in the form of an anhydrous purified powder, was added to the reactants and heated to the desired temperature. The following table lists the catalyst combinations found effective in reducing the amount of 2- phenyl isomer when alkylating benzene with chlorododecane. The ratio of AlCl to catalyst modifier is given in mole ratio except where a sulfonated styrene-divinyl benzene polymer is employed as the catalyst modifier and the ratio of AlCl to the polymer modifier is designated in a weight ratio.

TABLE Alkylation Catalyst Percent 2- I Mole ratio phenyl Friedelof A1013 Reaction isomer in crafts to modifier Temp time resulting component Modifier component component 0.) (min.) alkylate 65 60 28 2:1 65 50 24 1:4 65 60 26 1:4 65 6 25 1:4 65 13 26 1:1 60 30 26 1:4 65 66 25 1:14 65 65 25 1:20z5 65 60 25 1:10:23 80 60 25 Sulfonated styrene-divlnyl 85 60 24 benzene polymer. A101 Hexamethylbenzene 1:0. 5 65 90 25 A101 ..do 1:1 65 90 24 1 1 gm. 1.5 gm.

However, as previously mentioned, the preferred temperature range is determined according to the Friedel- Crafts catalyst constituent and the particular catalyst modifier constituent of the catalyst combination. For example, when aluminum chloride is employed as one constituent and either phenanthrene, durene, mesitylene, or zinc chloride is employed as the catalyst modifier it is preferred that the alkylation step be carried out at a temperature within the range of about 60 to 70 C. However, when either pyridine, hexamethylbenzene, or aluminum oxide is employed as the catalyst modifier the temperature in which the alkylation step is carried out is preferably within the range of 60 to 80 C. When employing a catalyst modifier having a two component mixture wherein one of the components is carbon tetrachloride and the other component is either phosphorus trichloride or boron oxide, the alkylation step is preferably carijied out at a temperature within the range of 60 to 85 C. However, when sulfuric acid is employed as the catalyst modifier the alkylation temperature is preferably carried out at a somewhat lower temperature, namely a temperature within the range of about 55 to 65 C. On the other hand, when a sulfontaed styrenedivinyl benzene polymer is employed as the catalyst modifier, it is preferred to carry out the alkylation step at a temperature within the range of about 80 to 90 C. in order to provide the desirable results wherein the reshlting straight-chain alkyl aryl compound contains a reduced amount of the isomer having the aryl nucleus attached at the two position of the alkyl chain.

In order to more fully illustrate the present invention, the following example is presented. However, it is to be understood that the example is for illustrative purposes only and as such should not be employed to unduly limit the scope of the present invention.

Thus, the above data clearly establishes that when employing the various modifiers listed above with a Friedel- Crafts catalyst, such as aluminum chloride, straight-chain alkyl aryl compounds containing a reduced amount of 2- phenyl isomer can be produced. However, when utilizing aluminum chloride alone as the catalyst with the identical chloroparaffin mixture one produces an alkylate with a 2-phenyl isomer content of 28 to 29 percent.

Various modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing description and example, and this invention should not be limited unduly to that set forth herein for illustrative purposes.

Having thus described the invention, we claim:

1. In an alkylation process for producing straight-chain alkyl aryl compounds wherein the the aromatic nuclei of aromatic compounds are alkylated with partially chlorinated straight-chain parafiins or straight-chain olefins in the presence of a Friedel-Crafts alkylation catalyst, the improvement which comprises alkylating said aromatic compounds with partially chlorinated C to C straightchain n-paraflins wherein from about 10 to 35 mole percent of the paraffins are chlorinated or with C to C straight-chain olefins in the presence of an alkylation catalyst combination of said Friedel-Crafts alkylation catalyst and a catalyst modifier selected] from the group consisting of pyridine, phenanthrene, durene, mesitylene, zinc chloride, sulfuric acid, aluminum oxide, phosphorous trichloride, carbon tetrachloride, boron oxide, hexamethylbenzene, and mixtures thereof, said Friedel-Crafts alkylation catalyst and said catalyst modifier being present in a mole ratio within the range of about 1:25 to 2:1, respectively, to provide resulting straight-chain alkyl aryl compounds containing a reduced amount of the isomer having the aryl nucleus attached at the two position of the alkyl chain.

2. The alkylation process according to claim 1 wherein the Friedel-Crafts alkylation catalyst is AlCl and the mole ratio of AlCl to partially chlorinated parafiin or olefin is within the range of about 1:15 to 1:30.

3. The alkylation process according to claim 2 wherein the alkylation step is carried out at a temperature within the range of about 60 to 70 C. and said catalyst modifiers are selected from the group consisting of phenanthrene, durene, mesitylene, and ZnCl and said AlCl alkylation catalyst and said catalyst modifiers are present in a mole ratio of about 1:4, respectively.

4. The alkylation process according to claim 2 wherein the alkylation step is carried out at a temperature within the range of about 60 to 80 C., said catalyst modifier is selected from the group consisting of pyridine, and hexamethylbenzene and said AlCl alkylation catalyst and said modifiers are present in a mole ratio of about 2: 1, respectively.

5. The alkylation process according to claim 2 wherein said alkylation step is carried out at a temperature within the range of about 60 to 85 C. and said catalyst modifier is a two component mixture wherein one component is carbon tetrachloride and the other component is selected from the group consisting of phosphorous trichloride and boron oxide.

6. The alkylation process according to claim 5 wherein said catalyst modifier is a mixture of carbon tetrachloride and phosphorus trichloride and said A101 alkylation catalyst, carbon tetrachloride and phosphorus trichloride are present in a mole ratio of about l:20:5, respectively.

7. The alkylation process according to claim 5 wherein said catalyst modifier is a mixture of carbon tetrachloride and boron oxide and said AlCl alkylation catalyst, carbon tetrachloride and boron oxide are present in a mole ratio of about 1:8: 10, respectively.

8. The alkylation process according to claim 2 wherein the alkylation step is carried out at a temperature within the range of about 55 to 65 C., said catalyst modifier issulfuric acid, and said A1Cl alkylation catalyst and said sulfuric acid are present in a mole ratio of about 1:1. 9. The alkylation process according to claim 2 wherein the alkylation step is carried out at a temperature within the range of about to C., said catalyst modifier is aluminum oxide, and said AlCl alkylation catalyst and said aluminum oxide are present in a mole ratio of abou 1:14, respectively. 10. In an alkylation process for producing straightchain alkyl aryl compounds wherein the aromatic nuclei of aromatic compounds are alkylated with partially chlorinated straight-chain parafiins or straight-chain olefinsin the presence of a Friedel-Crafts alkylation catalyst, the improvement which comprises alkylating said aromatic compound with partially chlorinated C to C straightchain paraffins wherein from about 10 to 35 mole percent of the paraffins are chlorinated or with C to C straight-chain olefins in the presence of an alkylation catalyst combination of said Friedel-Crafts alkylation catalysts and a sulfonated styrene-divinyl benzene polymer catalyst modifier, said Friedel-Crafts alkylation catalyst and said modifier being present in a weight ratio of about 1:1 to 1:2 to provide resulting straight-chain alkyl aryl compounds containing a reduced amount of an isomer having the aryl nucleus attached at the two position of References Cited UNITED STATES PATENTS 1/1968 Shook 260-671 6/1968 McEwan et a1. 260-671 DELBERT E. GANTZ, Primary Examiner C. R. DAVIS, Assistant Examiner 

